Ji Linhong

Professor, Department of Mechanical Engineering, Tsinghua University

Member of the Xinya College Teaching Committee, head of the CDIE discipline

Since the 1980s, Ji Linhong has been involved in the research and development of prosthetic limbs and rehabilitation aids for people with disabilities. At the 1992 Paralympic Games in Barcelona, Chinese athlete Sun Changting won gold wearing a sports prosthesis developed by Ji’s research lab. In 2018, the "Science and Technology for the Winter Olympics: Key Technologies for Improving the Athletic Performance of Winter Paralympic Athletes" initiative led by Ji was officially launched.

"Three Five-Star Red Flags were raised one after another!" On March 5, 2022, at the first awards ceremony of the Beijing Winter Paralympic Games, history was made. After a day of competion, Chinese athletes had won two gold, one silver, and two bronze medals. On March 6, Chinese athlete Liang Jingyi took home first place in the Men's Alpine Skiing Giant Slalom (standing category), marking the sixth gold won by the Chinese delegation.

Since the opening of the Beijing 2022 Winter Paralympics, Ji Linhong, member of the Chinese Disabled Cross-Country Skiing and Biathlon Team staff, professor in the Department of Mechanical Engineering at Tsinghua University, and adjunct professor at the Institute for Accessible Development at Tsinghua University, has been busy shuttling between competitions. The athletes’ achievements were “beyond expectations”.

In addition to the athletes' hard work and their coaches' effective guidance and support, there is another factor that must not be overlooked in the achievement of such good results: the power of technology.

In 2018, the project "Key Technologies for Improving the Athletic Performance of Winter Paralympic Athletes", a cornerstone of the "Science and Technology for the Winter Olympics" initiative headed by Professor Ji Linhong from the Department of Mechanical Engineering of Tsinghua University, was officially launched. The project was put forward by the China Disabled Persons' Federation and organized and implemented by the China Disabled Persons' Sports Management Centre. The project intended to provide an all-round technological guarantee for the graded selection of athletes, training monitoring, technical movement optimisation, special aids and equipment, injury prevention and rehabilitation, and more, to ensure that athletes could maximise their potential during training and competition.

"It's exceeded my wildest expectations!" At this point, the goals set by Professor Ji Linhong's team four years ago for the Winter Paralympic Games have all been achieved.

Team China's Yang Hongqiong in the Women's Cross-Country Skiing Long Distance (Sitting Division) Competition at the National Biathlon Centre during the for the Beijing 2022 Winter Paralympic Games on March 6

"No two ski racks are exactly the same"

With less than a month to go before the competition, the athletes' ski racks are still being repeatedly adjusted and replaced. In the test event, one athlete's ski rack slipped off, and another athlete's ski rack didn't feel comfortable enough to use. What could possibly be done?

"We rushed to redesign and recreate them, regardless of the cost," Ji Linhong said.

Paralympic athletes need special equipment and apparatus for competition and training, including prosthetic limbs, ski racks, sleds, helmets, donning aids, and protective gear. Ji Linhong is personally responsible for this part of the work. Ji told reporters, many of the race tracks and sportIng events in the Winter Paralympic Games are the same as those from the Winter Olympics. The biggest difference is that disabled athletes have different types of disabilities, such as lower limb amputations, lower limb muscle atrophy, and upper limb amputations. "The fact that everyone's circumstances are different poses the greatest challenge."

"No two athletes’ ski racks are exactly the same." Ji Linhong told reporters that many disabled athletes need to ski with the help of ski racks, and since athletes differ in terms of leg length, weight, exertion habits and so on, the size, centre of gravity, and other specifications of their ski racks must also differ. Therefore, each athlete's ski rack needs to be customized according to their individual circumstances.

Ski racks may look simple, but in the case of an athlete who is an amputee, their centre of gravity will likely be off; where must the centre of gravity of the ski rack lie for the athlete to maintain balance in left and right turns? Should it be forward-leaning or backward-leaning? The more resilient the material, the heavier it is; what material should be used to achieve resilience while maintaining a relatively light weight? Some athletes use their ski racks in a seated position, some in a kneeling position; how should the athlete and their rack be secured to the skis? All these details pose challenges for the design of ski racks.

According to Ji Linhong, the team attempted a quantitative evaluation of the design and use of the apparatuses, but in the end, they had to be adjusted based on the athletes’ experience and preferences to maximize their comfort and bring out their strengths.

The prosthetics used by disabled athletes in competition and training are also unique. For example, while snowboarding, athletes must bend their knees in a position similar to the horse stance. To achieve this, the knee joint and ankle joint of their prostheses are especially important: they must be flexibile, durable, and able to accurately sense the muscles activated by the athlete. "They must be practically capable of replacing human joints,” Ji Linhong said. Almost no Chinese ski prostheses exist that meet these requirements, and research is also lacking. At the same time, because the weight and strength of Chinese athletes are different from those of Western athletes, the resistance coefficients required for their equipment are different; as a result, equipment produced by foreign manufacturers is unsuitable for Chinese athletes. Consequently, Ji Linhong and his team decided to develop all the technology from scratch. "Although the design principles were clear, the specifics of how to adjust the resistance, stiffness, and responsivity required further research."

Improving muscle strength asymmetries and making up for the "shortcomings" of athletes

“Just how much could we improve athletes’ performance by helping them overcome their shortcomings?” Ji and his team came up with this idea during the training period for the Winter Paralympics. They hypothesized that while most athletes tend to focus on event-specific skills during training, they would benefit more from targeting their “shortcomings” first.

To achieve this, Ji Linhong’s team developed an experimental platform to collect and monitor data from athletes during training using motion sensors, including body parameters, metabolism, muscle power, exertion effect, and more, utilizing quantitative results to optimise athletes' movements and strength. During the training process, Ji Linhong found that some athletes would suffer from back pain and shoulder pain. Upon further investigation, it was found that this phenomenon could not be explained by sports injury alone, but was likely due to disabilities causing the athletes to have insufficient strength in certain muscles. Later, the team took a census of the athletes to see if they had anterior pelvic tilt or scapular instability.

"For example, if you have a single leg amputation, you often walk on one leg, so the muscles on that leg are particularly strong, while the muscles on the other side are weak. This is called muscle asymmetry." Ji Linhong explained that in everyday situations, this is not a problem, but in sports and in situations of extreme exertion, it can cause as a major problem.

To make up for athletes’ core muscle strength asymmetries, the team developed a targeted training plan for each athlete. An athlete missing one upper limb was given a prosthetic limb and made to do push-ups to train the muscles on that side; an athlete missing a lower limb who was only using one leg for power was given a prosthetic limb to train them to use both sides at the same time so that the muscles on both sides could develop evenly.

"The problem of muscle asymmetry is solved and the athlete's overall athletic ability is much improved. We've done some targeted training over the past few years and it's worked well." This research is currently unique to China.

In addition, some athletes who suffer from polio or paraplegia have abnormal peripheral nerves or poor blood circulation, resulting in dulled perception. "They can't feel the cold—by the time they feel it, they’ve already got frostbite," Ji Linhong said. In the wheelchair curling event, each game lasts two to three hours. "The athletes definitely get cold sitting in their wheelchairs, but wearing too much can affect their movements. It's a contradiction." Ji Linhong began to wonder how he could make it possible for the athletes not to have to wear too much and also avoid frostbite. Pushing curling stones requires athletes to be highly sensitive, and if they get frostbite, or if other parts of their body are uncomfortable, it can affect their performance.

"We want every part of the athlete's body to remain in a comfortable and stable condition." Ji Linhong said that in this situation, it was necessary to help the athletes warm up. For this purpose, the team chose heating and insulation materials to be added to the athletes' clothes and shoes, utilizing graphene materials and infrared reflection technology to improve heating efficiency and insulation performance.

A breakthrough in the number of participants and medals

"Athletics is a very cruel thing. You have to find the right athlete and use the right method to stimulate their abilities to the right degree," Ji Linhong said.

Many able-bodied athletes start training as children and grow up to compete in international competitions, and the athletes themselves know their training methods very well. On the other hand, the vast majority of Paralympic athletes have never skied prior to joining the Paralympic games, and their knowledge of the sport is lacking. Because of this, Ji Linhong pointed out, the biggest challenge is to turn amateur athletes into athletes, athletes into professionals, and finally professional athletes into skilled competitive athletes.

Disabled athletes need the assistance of equipment to undertake their sport. Ji Linhong’s team has worked hard to maximize compatibility between athletes' abilities and the capacities of the equipment. "We try to turn the apparatus into a part of the person."

To ensure fairness and impartiality, the IPC has strict standards and regulations for the assistive devices used by Winter Paralympic athletes, including specifications and weights. “Equipment powered by springs or motors is definitely not allowed." Therefore, though equipment is important, it ultimately only plays an auxiliary role; what’s most important is the athletes’ own ability, as well as their compatibility with the equipment, such that they can achieve their maximum potential.

In previous Winter Paralympic Games, Team China often consisted of only one or two dozen participants, and the events they participated in were few and far between. Prior to Beijing 2022, Team China had only won one gold medal in wheelchair curling, and only 12 competitors ever reached the top eight in their event. Therefore, at the start of the project in 2018, Ji Linhong's team set two goals for the 2022 Beijing Winter Paralympics: firstly, to increase the number of athletes qualifying for the Paralympics by 50% to over 40, and secondly, to achieve the historic breakthrough of raising the Chinese flag and playing the national anthem at an awards ceremony.

At present, the number of participants in the Chinese Paralympic delegation has already doubled. Official figures indicate that 96 athletes from Team China are to compete in this year's Winter Paralympics, of which 85 will be competing in the Winter Paralympics for the first time. This is Team China’s largest delegation in terms of number of participants and registered events since China first entered the Winter Paralympics. As for results, as of March 6, Team China has achieved exceptional results in the two major events of cross-country skiing and alpine skiing, and has already won 6 gold, 4 silver, and 6 bronze medals in the two days since the games opened, ranking first as of now on the medal table. At this point, both goals set by Ji Linhong and his team have been achieved.

But Ji Linhong has one more goal: using the insights he gained from Team China at the Beijing 2022 Winter Paralympics, Ji aims to create a comprehensive set of technologies for the competition and training of Chinese athletes with disabilities. In the future, Ji hopes to shape an open and sustainable environment for people with disabilities to continue enjoying winter sports. “In the past, all of this was a blank slate.”

Source: Xinjing News, Tsinghua University Department of Mechanical Engineering official account